Power mast and boom hoist



Feb. 20, 1945. B. M. CRAWFORD- POWER-MAST AND BOOM HOIST 3 Sheets-Sheet 1.

Filed July 17, 1943 .114. CEAWF'ORD,

INVENTOR.

ATTORN EY.

Feb. 20, 1945. y M CRAWFORD 2,369,816

POWER MAST AND BOOM HOIST Filed July 17, 1943 3 Sheets-Sheet 2 IN V ENTOR. BEA 77') M CPA wroeo,

ATTORN EY.

Patented Feb. 20, 1945 UNITED STATES" PAENT FF-1on3" 2,369,816 I I POWER MAST AND BOOM HOIST Beatty M. Crawford, Santa Ana, Calif. Application July 17, 1943, Serial No. 495,185 18 Claims. (01. 212-63) This invention relates to improvements in power hoists and may be regarded as an improvement overthe power hoist disclosed in my prior United States Letters Patent No. 2,101,839 issued December'li, 1937'.

' In the above-numbered patentthere is disclosed a power hoist for use on trucks and the like wherein'there is an extensible mastcarrying a boom at its upper end whichprovides a track on which a carriage or travelling block may move. Provision is made for removing the carriage or travelling blockfrom the track on the boom and operating it therefrom so as to enable the traveling block or carriage to be lowered to a position that may be materially below the floor or the trucl; for loading and unloading purposes. The raising; and lowering of the mast and the raising and lowering of the travelling block when suspended from the boom is accomplished by means of a single cable which may be wound upon and unwound from a power-driven winch, the'power oi, which maybe suppliedfrom any suitable source or power such he engine of the truck.

In the construction disclosed in the above-numbored patentwhen the carriage or travelling block is positioned on the track of the boom, inward and outwardmovements of the carriage along the length of the boom must be accomplished manually and where the loads are quite heavy, this manual movement is sometimesquite di-flicult.

An object of the present invention is to provide an improved power hoist having an extensible mast and, a boom with a carriage ortravel travelling block may be arrested selectively at 'variousstations.

Another object of the invention is to provide a powenhoist having the above-mentioned char-- acteristics wherein the mast and boom thereon may be turned by a power-source so as to swing the boom over the desired location where the load may be or where it may be desirable to de posit the load.

With-the foregoing and other objects in view, which will be made manifest in the following detailed description and specifically pointed out in the appended claims, reference is had'to the ac companying drawings for an illustrative embodi ment of the invention wherein:

Figure 1 is a view in side elevation of the power hoist embodying the present invention;

Fig. 2 is avertical sectionthrough the power hoist illustrating it inthat position wherein a load is about to be picked'up from the floor of the truck and unloaded therefrom;

Fig. 3 is a partial view in vertical section simi lartoJFig.2; illustrating the hoist in that p'osi tion'assumed by 'th'e"par'ts. after the mast has ling; block that can be transferred to and from the boom and which, when transferred from the boom, is suspend'ed therefrom. The raisingand eliminating manual shifting along the length-of the boom which, asv above-explained, is awkward and difficult.

Specifically, an object, or theinvention is to provide a power hoist having an extensible mast, a boom, a travelling block that maybe, trans; ferred to and from the boom and whentransferred from the boom the travelling blockis suspended therefrom, and to provide a single, cable operatin means for hoisting the travelling block to the boom, positioning it thereon, draw ing it inwardly on the boom and also eilectingfa raising and lowering oi the mast. Another object of the invention isto provide a power hoist having theabove-mentioned characteristics wherein inward movements of the been extended inperformi'ng' the unloading operatiomh, r

Figs. 4 and 5 are horizontal sections taken substantiallyupon the lines 4'-4; and 5-5, respectively, on Fig. 2; 1 I

Fig. 6 is a vertical section taken substantially upon the line 6--B upon Fig. 2 in the direction indicated;

Fig. 7 is a view similar to Fig. 2, but-illustrating'the travelling block or carriage as having been transferred from the boom and suspended therefrom;

' Fig. 8 is a top plan view of the boom; and

Figs. 9 and 1c are'horizontal sections taken substantially upon the lines 99 and llllil of Fig. '7,- respectively. I

Referring to the accompanying drawings wherein similar'reference characters designate similar parts throughout, the improved power hoist comprises an, extensible mast which may be mounted on the floor of a truck, on the floor of a loading dock, or on a deck. It comprises an outer housing l0 associated with which may be a power-driven winch, generally designated at H, on which may be wound up a cable 12.

The winch ll may be of any suitable construchowever, may be employed to operate the winch.

Within the housing Ill there is disposed an outer sleeve 3 which rests at its bottom on the bottom of the housing and which may be rotated therein. On the lower end of the sleeve l3 there is provided an external worm gear |4 "meshing with a worm 45 which can be driven formed segmental threads II; which mesh with threads N that are formed on the exterior of an inner sleeve I8. Thus by rotating worm |5 and consequently rotating sleeve i3, the inner sleeve I8 can be raised or lowered to any adjusted position desired.

.Within the inner sleeve I8 there is disposed an I-beam or H-column l9 which has a recess 20 adjacent its lower end to accommodate a grooved roller 2|, see Fig. 5, that bears against the interior of the inner sleeve Hi. The upper end of the I-beam or H-column carries a'boom, particularly designated 22, which extends outwardly and slightly downwardly from the I-beam on the opposite side thereof from that side on which the roller 2| is located.

The means for raising and lowering the extensible mast formed by the outer sleeve l3, the inner sleeve l8, and the I-beam I9 is as follows: On the bottom of housing l0 there is mounted a sheave 23 over which the cable I2 is trained. Near the upper end of the inner sleeve I8 there are disposed two stub. shafts 24 and 25, see Fig. 9. which extend inwardly toward opposite sides of the I-beam l3. Sheaves 2B and 21 are rotatably mounted on these stub shafts. Near the bottom of the I-beam IS the web of the I-beam is removed to accommodate a shaft 28, see Figs. 2 and 4, on which sheaves 29 and 30 are rotatably mounted. These sheaves are consequently rotatable about axes which are in planes at right angles to the axes of rotation of the two upper sheaves 26 and 21. The cable |2 after passing around sheave 23 extends upwardly around sheave 21, then downwardly around sheave 29, upwardly around sheave 26, downwardly around sheave 30, and finally upward around a sheave 3| which is rotatably mounted as at 32 on the boom.

If the upper end of the cable I 2, where it passes around sheave 3| is held stationary and the lower end of the cable l2, where it passes around 23, is pulled the four sheaves 26, 21, 29, and 30 function as a four-pulley hoist raising the I-beam within the inner sleeve l8 and consequently elevating the boom 22 that is mounted thereon.

Conversely, if the mast is in its extended or elevated position paying out of the cable |2 will allow the mast to lower and thus allow the I- beam l9 to recede or descend within the inner sleeve l8.

It is desirable to be able to lock the mast in its elevated or extended position, and to this end the inner ends of the stub shafts 24 and 25 are recessed or cut away at substantially a diameter as indicated at 33. Looking bars 34 and 35 are provided which have recesses 36 adjacent the upper ends by which they are swingably mounted from'the boom. These locking bars have at their lower ends outwardly extending fingers 31 above which there are shoulders 38. Upward movement of the I-beam l9 relative to sleeve i8 is limited by the fingers 31 on the locking bars 34 and 35 engaging the undersides of the inner ends of the stub shafts 24 and 25 as illustrated in Fig. 3.

If the locking bars are swung from the vertical, as illustrated in Fig. 3, and the I-beam is allowed to descend a short distance the shoulders 38 will engage the upper sides of the inner ends bars.

of the stub shafts 24 and 25 and thus lock the I-beam in extended position, holding it in its elevated position regardless of the tension applied to the cable l2.

A spacer 39 is positioned between the upper end of sleeve l8 and the I-beamand forms a guide or bearing against which the I-beam or H-column may slide during its upward and downward movements.

The boom, generally indicated at 22, is also formed from an I-beam, the flanges of which are indicated at 4B and 4|, see Fig. 6, and the web of which is indicated at 42. The top edges of the flanges provide rails or a track for the carriage or travelling block. On the web there is slidably positioned a T bar 43, the flanges of which are slotted as at 44 to receive bolts 45. This T bar is slidable on the web 42 within limits defined by the ends of the slots 44. Tension springs 46 are connected to the T bar and to some of the bolts 45, and urge the T bar toward the right as viewed in Figs, 2, 3, and 8. The upstanding central vertical web of the T bar indicated at 41 has a series of inclined notches 48 formed therein and adjacent the inner end of the T bar there are communicating downwardly divergent notches 50 and 5| A leaf spring 52 has a finger 53 which, as shown in Figs. 2 and 7, is disposed in the bottom of notch 50, This spring slidably extends through recesses 54 in the opposed faces of the locking bars 34 and 35. A spring latch 55 has a boss 56 thereon which is receivable in either of two grooves 5101" 58 formed on top of the locking Thus, in the position shown in Figs. 2, 3 and 7, the boss 56 is disposed in recess 5?. It is possible, however, to spring latch 55 upwardly and then slide the leaf spring 52 toward the right and position boss 56 in recess 58.

The outer end of the web 42 is cut away to accommodate a sheave 59 between the outer ends of the side flanges on the boom. This sheave is rotatably mounted on a pintle 60 and is adapted to have the cable I2 pass thereover when the carriage or travelling block is suspended from the boom, as shown in Fig. '7. Adjacent the outer end of the flange 4| on the boom there is secured an upwardly and outwardly extending arm or bracket 5|. This bracket provides an upper pair of spaced short rails 62 and 33 for rollers 84 and 65 that are rotatable on an axle 55, which extend through an upper sheave 51. At the ends oi these rails there are stops 68 that are engageable by the rollers to limit outward movement of the rollers and of the upper sheave. The carriage or travelling block consists of a suitable body 59 to the top of which one end of the cable |2 is anchored as at 10. This end of the cable is trained about the upper sheave 51 and then around a travelling block sheave or pulley YI rotatably mounted on the center of a large wheel or rollers 12 that is rotatable upon an axle 13,. This wheel or roller is flanged and serves to roll upon the top edges of the flanges 0r rails 46 and 4|. The bottom of body 69 may be equipped with a swivel hook 14.

On the top of housing ii) there is an insulated conductor rin 15 engageable by a brush 16 regardless of the position to which the outer sleeve l3 may have been turned. This brush in turnis electrically connected to a brush Ti engageable with a conductor strip 78 mounted on the I-beam or H-column. On the outer side oi flange40 of the boom, see Fig. 6, there is a conductor strip 19 to which conductor stri 78 v mally retracted posiition is-.-eiemim1s= connected; Thisreonductmz strip is eneageablez by as brush so on the:- inside at the winding: of. the cable: isefiective to pull the. traveltravelling block body 69. Brush 80 is electrically connected to a solenoid 8| disposed on the outer side oi'the travelling block body; This solenoid when energized serves: tomagneticaliy attract an armature- 82 on) alatch 83: to swing itdownwardly for: engagement: with one of the. notches 9i A tension springflfi urges the latch into nor- At the tone! the outersleeve l 3 the sleeveis notchedand may be provided with outwardly extending" ears 85. Semi-circular clampingelements 86, see-Figill); areequipped with ears 81 extending outwardly-through the notches. These ears areadapted to: be tightened togetheras by a tightening bolts. 88. f The clamping elements are disposed between the outer sleeve l3- and the inner sleeve I8 and when tightened they serve to lock them-nor sleeve against rotation whenever qccasionrequires; v

Assuming that it is'd esirableto unloadfrom the bod-yof the truck and deposit the loada-lower elevation, suchas on" the adjacent ground, the hoist is initially positioned in the position shown in Fig. 2, wherein boss 56' is dis posed in recess 51; A hitch placed aboutthe load is'attached tothe'swivel hook 1'4 andtension is applied to=-the cable l2; This initial tension tends note-h 5.0 bending the outer arm of the spring 5''! upwardly and: thus urging thelock lip-bars 3 lf and.35 tc swing; outwardly. The mast may.

be elevated by the continued taking in of cable [2; 0n thewin'ch until the. fingers 3T engage the inner endsof the stub shafts- M and 25, as shown on Fig. 3:. When the stub shafts pass over the shoulders 38; the biased spring; 52 causes the lockeupbars to swing outwardly as shown in Fig. 3. The cable 12 can then 'bepa-id outwardh;

slowly; allowing themast to settle untii shoul ders 38 engage the inner ends of'thefstub shafts and thus lock the mast. in extended position.

further paying out: of the cable I2 allows the carriage or travelling block .to lower down the slightly inclined boo-m. As the travelling bl'ocl'r reaches the. end. of" the boom, rollersfifiand G5 7 engage and roll on the upper rails. 62 and 6.3: as

indicated in. dotted lines on Fig. 2. Continued paying out. oithe cable allows the travelling block to. descend, it being; understood. that it is their;

7 suspended'f'rom. the upper sheave 61 which is supported by rollers 6d and 65 on. rails 62 and. 63 against the. stubs 6.8.. The cables can then be paid out as far as is necessary to lower the'carriage or travelling block any required distance to deposit the load on the ground, see Fig. 7. When the load is detached from the swivel hook T4" the cable is again wound upon the winch serving to first elevate the travellingblock upwardly until the top of the body 65' engages'the bottom of sheave 61. Preferably there'is a bed or ridge 9!) formed on the top of the body 619 that fits between the flanges: of the sheave ill to seat the sheave 61 thereon. When the-toprof thebody-i is has engaged the sheaveii 'l further boom. sheave and: its associated rollers: 64 and; Blithen move with'thebody 69 of the: travel.- ling block as one as. shown in Fig.2. The travelling block is: moved inwardly until it. engages a. stopttzeon 'the under side, of the boom, thus. arresting: inward movement of the travelling; block. causing further takeup of. the cable. t2; to. raise the mastso that the inner ends of the stub. shafts: .245 and will disengage shoulders 38... During this inward; movement of the. travelling block. it will be noted. that, the T bar '43,- is; not disturbed. Hence it will remain in its; retracted. position under the influence-oi springs; Mi. Finger 53: will consequently be at the-bottom of: slot or. recess: 50... Spring. 52 will consequently notv be: biased and will allow the lock up bars 3.4 and: to hang vertically. The cable? 12 may then be paid. out to lower the mast and the boom; tov pick up. another loadfrom: the floor. of the truck. to be unloaded A second load may then be attached to the swivel hook I la-rid the cycle of operation be repeated.

If it is desired to load the truck ire-m the ground 'a slight adjustment. is. made. The spring latch 55 is sprung upwardly and the leaf spring 52 is caused. to slide outwardly. Boss 53 is positioned in recess 58.. This. outward: sliding. movement of spring 52 positions itsflnger 53 at the top of the juncture of the two divergent recesses and SI. Consequently, afterv this adjustment has been made the. spring. 52 is. biased to urge the loo-king bars. 3.4. and 35 outwardly when: the T bar 43 is in its retracted. position. To. pick: up a-load from the ground, the cable is first wound up on the winch. drawing the: travelling block. into engagement. withstop tl. This. elevates. the mast and when. the mast iS;.iIIsi-lis uppermost position on passing; out the; cable. the locking. bars will engage the. stubshafts- 24 and. 7.95 it being understood that thisvis nowaccomplished by reason of the fact that. spring 52: is. normally biased to swing the locking bars outwardly. Further passing out of the cable: allows the travelling block to move out wardly on the-boom and. to be suspended; from the. upper shear/e61: when it isv supported on the bracket iii. The travelling block can then be allowed to descend and be connected to the load. The cable: I'Z'isthen wound up on the Winch lifting the: load and transferring the traveling block onto the boom. Asthe travelling block is pulled inwardly" onthe boom the electrical, circuit througlrthe solenoid 8| is closed at the proper or desired location, causing latch 83- to swing downwardly into one of the notches 49. This arrests inward. movement-of the travelling block or carriage when. the T bar has been caused to slide inwardly, to theiend of; its .movementas governed by:the.= lengths of the. slots 44. When the. T bar has been thus moved inwardly finger 53 has moved. to the bottom of the notch or slot 5| unbiasing: spring 52 so that the lockup bars 34 and 35' willztend to hang vertically. Usually the arresting of the movement of the carriage or travelling block takesplace. slightly before the winding up. of the cable. 12 has ceased that the mast will be elevated slightly after-the inward movement of the. traveling block has stopped. This lifts shoulder 38 out of engagement with the stub shafts 24 and: 25,. Thecable is then paid out allowing the mast. to. descendorcollapse and thus deposit the. load on the floor of the truck. To pick up a succeeding load, the cable 12 is paid out. to allow: a slight backward muvementof the travelling blockso that latch 83 will no'longer bind or be held in the notch that it may have engaged. When the latch is thus released its spring serves to completely disengage the latch from the notched bar on the boom. On winding up the cable I2 on the winch the travelling block may be brought into engagement with stop 92. the mast elevated, and locked up as in Fig. 3. Note that under these circumstances finger 53 will be at the top of notch or slot thus biasing the spring 52 to urge the lock up bars 34 and 35 into locking position. When the mast ha been locked up in elevated position the carriage or travelling block is allowed to descend on the inclined boom and to be suspended therefrom as shown in Fig. 7, to pick up a succeeding load.

During some loading or unloading it-is possible to turn the mast and boom thereon by hand. However, the present construction enables power to be utilized for this purpose. This is accomplished by clamping up the clamping means 85, 86, 8'1, and 88 to lock the sleeves l8 and I3 together. The cars 85 of the clamp merely serve to hold the clamping members in place. The clamp members 88 are tightened or loosened by tightening or loosening bolt 88 extending through cars 81. These members when tightened lock the sleeves l8 and 13 together. When these sleeves are locked together on rotating worm l5 the mast turns as a unitary structure.

In some instances, the load is either loaded or unloaded in tiers. If the inner sleeve i8 is in its lowermost position, as shown on Fig. 2, the construction is susceptible of loading or unloading a lower tier. However, if it is desired to load or unload an upper tier the hoist may be adjusted for this purpose by holding the inner sleeve l8 against rotation and rotating the outer sleeve 13 by the Worm. This causes the screw teeth or threads. I! to climb the segmental threads 18 elevating sleeve l8, and the contained structure to a higher position than that shown. When so adjusted the construction may be operated the same as previously explained.

Proper practice is to adjust the mast to the desired height to handle conveniently the maximum height of the load to be handled. A' chain or sling is used to connect the load to swivel hook l4 and if the load consists of cotton bales, the structure is adjusted so as to conveniently deposit a layer or tier of cotton bales on the floor of the truck. The chain or sling can then be hooked up or shortened to accommodate succeeding layers or tiers of cotton bales to be loaded. The sling can be shortened or lengthened in a similar manner in unloading.

It will be appreciated that the improved power hoist is of simple and sturdy design. It is very fast in operation, facilitating loading and unloading. While the construction has been primarily designed for use on trucks, such as are adapted to carry cotton bales, it will be appreciated that it may be employed wherever there is occasion to raise and shift heavy loads. The improved construction is advantageous in that the power applied to the cable I2 is used not only to raise and lower the load onto and ofi of the boom, but is also utilized to pull the carriage or travelling block inwardly on the boom to the desired location. Outward movements of the carriage or travelling block are accomplished by allowing the travelling block to merely roll down the inclined boom toward its outer end'until such movement is arrested by the cable.

Various changes may be made inthe details of construction without departing from the spirit or scope; of the invention as defined by appended claims.

I claim:

l. A device of the class described comprising an extensible mast, a boom mounted thereon adjacent its upper end, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom so that the block may be suspended therefrom, and a cable extending up the mast around the block and around said pulley and anchored to the block adapted to lift the block to the boom and then pull the block and pulley inwardly thereon.

2. A device of the class described comprising an extensible mast, a boom mounted thereon adjacent its upper end, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom so that the block may be suspended therefrom, a cable extending up the mast around the block and around said pulley and anchored to the block adapted to lift the block to the boom and then pull the block and pulley inwardly thereon, and means forarresting the inward movement of the block on the boom.

3. A device or" the class described comprising an extensible mast, a boom mounted thereon adjacent its upper'end, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom so that the block may be suspended therefrom, a cable extending up the mast around the block and around said pulley and anchored to the block adapted to lift the block to the boom and then pull the block and pulley inwardly thereon, and means for arresting the inward movement of the block on the boom at various locations.

4. A device of the class described comprising an extensible mast a boom mounted thereon adjacent its upper end, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom so that the block may be suspended therefrom, and a cable extending up the mast around the block and around said pulley and anchored to the block adapted to lift the block to the boom and then pull the block and pulley inwardly thereon, there being pulleys on the mast over which the cable is trained whereby tension on the cable may serve to elevate the mast.

5. A device of the class described comprising an extensible mast, a boom mounted thereon adjacent its upper end, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom so that the block may be suspended therefrom, a cable extending up the mast around the block and around said pulley and anchored to the block adapted to lift the block to the boom and then pull the block and pulley inwardly thereon, there being pulleys on the mast over which the cable is trained whereby tension on the cable may serve to elevate the mast, and means for locking the mast in extended position.

6. A device of the class described comprising an extensible mast, a boom mounted thereon adjacent its upper end, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom so that the block may be suspended therefrom, a cable extending up the mast around the block and around said pulley and anchored to the block adapted to lift the block to the boom and then pull. the block and pulley inwardly thereon,

there being pulleys on the, mast over which the cable is trained whereby tension on the cable may serve to elevate the mast, and means for locking the mast in extended position, operablev by the means serving to arrest inward movement of the block.

'7. A device of the class described comprising an extensible mast, a downwardly and outwardly inclined boom mounted thereon adjacent its upper end, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom 50 that the block may'be suspended therefrom, and a cable extending up the mast around the block, around said pulley, and anchored to the block adapted to lift the block to the boom and then pull the block and pulley inwardly thereon, means on the boom for arresting inward movements of the block, and a latch on the block engageable with said means. i

'8. A device of the class described comprising an extensible mast, a boom mounted thereon, a block movable along the length of the boom, means for locking and unlocking the mast-in extended position, and means operable by the block on the boom for operating the last-men- I tioned means.

9. A device of the class described comprising an extensible mast, said mast having an outer 10. A device of the class described comprising an extensible mast, said mast having an outer housing, an outer sleeve disposed therein, an inner sleeve in threaded engagement with the outer sleeve, a mast section slidablydisposed within the inner sleeve, sheaves n the inner sleeve and mast section, a cable trained over the sheaves, a block, a boom on the mast along which the block is movable, said cable being connected to said block and serving when pulled to elevate the mast and pull the block inwardly on the boom, and means for rotating the outer sleeve.

11. A device of the class described comprising an extensible mast, said mast having an outer housing, an outer sleeve disposed therein, an inner sleeve in threaded engagement with the outer sleeve, a mast section slidablydisposed within the inner sleeve, sheaves on the inner'sleeve and mast section, a cable trained over the sheaves, a block, a boom on the mast along which the block is movable, said cable being connected to said block and serving when pulled to elevate the mast and pull the block inwardly on the boom, and means for rotating the outer sleeve, and means for locking the outer sleeve andinner sleeve together.

engageable by the block for operating the lockup bars to either lock or unlock the mast against collapse.

13. A device of the class described comprising a mast, a boom mounted thereon adjacent its upper 'end, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom so that the block may be suspended therefrom, and a cable extending up the mast outwardly along the boom around the block and said pulley and anchored to the block adapted to lift the block to the boom, and then pull the block and pulley inwardly thereon.

14. A device of the class described comprising a mast, a boom mounted thereon adjacent its upperend, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boo-m so that the block may be suspended therefrom, a cable extending up the mast outwardly along the boom around the block and said pulley and anchored to the block adapted to lift the block to the boom and then .pull the block and pulley inwardly thereon, and

means on the boom for arresting inward movements of the block on the boom.

15. A device of the class described comprising a mast, a boom mounted thereon adjacent its upper end, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom so that the block may be suspended therefrom, a cable extending up the mast outwardly along the boom around the block and said pulleyand anchored to the block adapted to lift the block to the boom, and then pull the block and pulley inwardly thereon, means on the boom for arresting inward movements of the block on the boom, and a latch on the block engageable with said means.

16. In a device of the class described, a boom, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom adjacent the outer end thereof so that the block may be suspended therefrom, and a cable extending along the length of the mast around the block and around said pulley adapted to lift the block to the boom and then pull the block and pulley inwardly thereon.

17. In a device of theclass described, a boom, a block movable along the length of the boom, a pulleyon the block, means for supporting the pulley on the boom adjacent the outer end thereof so that the block may be suspended therefrom, a cable extending along the length of the mast around the block and around said pulley adapted to lift the block to the boom and then pull the block and pulley inwardly thereon, ,and means on the boom for arresting inward movements of the block.

18. In a device of the class described, a boom, a block movable along the length of the boom, a pulley on the block, means for supporting the pulley on the boom adjacent the outer end thereof so that the block may be suspended therefrom, a

cable extending along the length of the mast around the block and around said pulley adapted to lift the block to the boom and then pull the block and pulley inwardly thereon, means on the boom for arresting inward movements of the block, and a latch on the block engageable with said means.

- BEATTY M. CRAWFORD. 

